Bobbin holders have been utilized in conventional yarn winding apparatus for supporting bobbins from the inside thereof. Typical bobbin holders utilized at a high speed have coned disc members made of metallic material and inserted onto a holder body, i.e., rotatable spindle. The coned disc members are axially urged to radially expand when they hold bobbins, and they are axially retracted to radially reduce when they release bobbins.
However, such conventional bobbin holders have a defect that they easily damage the inner surfaces of bobbins because of the following reasons.
Since the coned disc members are made of metallic material which is harder than paper or plastic, of which bobbins are made, the coned disc members damage the inner surfaces of the bobbins.
Since metallic material, of which coned disc members are made, have a large specific weight, it is necessary to reduce the thickness of the coned disc members in order to reduce their weight. The contacting area between the coned disc members and the bobbins becomes small, when the thickness of the coned disc members is reduced, and accordingly, the pressure exerted at the contacting area increases. As a result, the bobbin made of paper or plastic is easily damaged.
Because of the above-described reasons, bobbins are often damaged by the metallic coned disc members utilized in conventional bobbin holders, especially when such conventional yarn winding apparatus are utilized for a high speed winding, wherein the yarn winding speed exceed 4,000 m/min, due to the centrifugal force. In addition, the coned disc members frequently result in the deformation of bobbins due to the centrifugal force and adversely affect the quality of yarn wound on the bobbin.
In addition to the above-described defect, the above-described conventional bobbin holders also have a defect that they are damaged and ruptured due to the centrifugal force when they are rotated while an operator forgets to insert a bobbin thereonto.